Slide projectors utilizing circular magazines are well known. Generally, the circular magazine carrying individual slides in separate compartments is rotated in a stepwise manner by a suitable gear unit to bring the individual slides sequentially into position for removal. Usually, the circular magazine can be loosely inserted into the slide projector. The drive connection between the circular magazine and the gear unit is effected in such known systems either by cams provided on the outer edge of the circular magazine which cooperate with suitable gear components, or by a gear rim formed at the base of the magazine or on its peripheral surface which meshes with a drive component such as a pinion when the circular magazine is placed into the projector housing. Such known slide projectors differ from one another in the maximum number of slides which can be carried in their circular magazine. Since the external diameters of the various known circular magazines generally are equal, the circumferential length of each turning step is necessarily different for different magazines depending upon the maximum number of slides carried. For example, for a circular magazine capable of carrying 80 slides, the actual length of the circumferential step must be greater than for a circular magazine capable of carrying 120 slides in order that each successive slide be brought into proper position for removal.
For this reason, it has not been possible until the present invention to use, in the same slide projector, circular magazines from different manufacturers or with a different maximum number of slides carried. One of the most widely used circular magazines consists of an approximately flat circular sheet metal base plate upon the upper part of the magazine is rotatably fixed with compartments for 140 slides. A device interconnects the base plate with the upper part of the magazine. The bolt of the locking device is spring-loaded and extends between teeth which are formed on a gear rim disposed on the inner wall of the upper part of the magazine. A suitable notch is provided on the outside wall of the upper part of the magazine. In the case of another frequently used circular magazine, an approximately flat base plate having a removal slot for the individual slides is rotatably disposed with respect to the upper part of the magazine which has 80 individual compartments for slides. In order to rotate the slides individually to a position over the removal slot in the base plate, a large number of lugs is provided in regularly spaced relation on the upper part of the magazine radially outside of the base plate and these lugs form a continuous gear rim. To rotate the upper part of the magazine, a finger coupled by a gear to the drive motor engages the gear rim between two lugs, and when a corresponding switch on the upper part of the magazine is actuated, the finger rotates the upper part by one step.
It is obvious that each of the previously described circular magazines is suitable only for a particular projector whose drive system is specifically adapted for the design of the circular magazine. In practice, users are forced to utilize only magazines with projectors which are designed for each other. This result is especially disadvantageous for those users who have several projectors and a large number of magazines, as is frequently the case in schools and universities. Previously, when a newer slide projector was obtained to replace equipment which was damaged or worn out, it was necessary to remove the individual slides from the old magazines by hand and to place them into the new magazine, a procedure which is not only troublesome, butwhich is quite time consuming.